Recent trends have developed two major factors in the design of industrial facilities, i.e., the increasingly stringent governmental pollution control requirements, and the cost and availability of energy. Particularly difficult problems in this regard are found in the design of paint spray booth facilities for the application of paint to automative bodies and similar products, due to the enormous volumes of air flow required in the paint spray booths in industry.
The pollution problems are associated primarily with the hydrocarbon liquid constituents, including solvents, thinners and diluents of acrylic and lacquer paints and enamels. Such liquid constituents are vaporized during the paint application, as well as paint drying which vapors pass into air ciculated through the booth. Such air must be circulated at relatively high volume in order to enable the paint sprayers to work in a healthful and clean environment.
The rigorous standards of emissions applied to industrial facilities precludes the discharge of such hydrocarbon or solvent laden air directly into the atmosphere, and such vapors in the discharged air are required to be reduced to very low levels.
A common approach in eliminating such vapors which are combustible is to incinerate the same by passing the air into an incineration chamber which is heated by a burner to raise the temperature of the air sufficiently to cause oxidation of the hydrocarbons into carbon dioxide and water vapor prior to being exhausted by the atmosphere.
However, for the enormous air flow rates exhausted from paint spraying booths, the incineration process requires vast expenditures of energy, thus rendering this solution very costly to implement.
Another alternate approach which has been attempted and considered in this context is the use of adsorber beds such as of activated charcoal, over which the exhaust air is passed for direct adsorption of the solvent vapors, thus enabling their elimination from the exhaust air.
Again, the enormous air volumes in automotive production and similar applications and the need to regenerate the adsorber beds render this approach extremely expensive.
Yet another approach which has been proposed involves the replacement of the hydrocarbon solvent based paint with water based paint, the elimination of vapors thus enabling direct discharge of the exhaust air to the atmosphere, after filtration or other treatment of the air to remove the paint solids.
While effective in this regard, the water based paints require close control over the temperature and humidity of the air supplied to the booth, with air cooling and dehumidification during summertime, and heating and humidification during wintertime operation. This requirement requires considerable capital investment and furthermore entails considerable energy to execute.
Accordingly, it is an object of the present invention to provide a system and process for the elimination of hydrocarbon vapors from the air exhausted from a paint spray facility in which the equipment required is relatively modest and in which the energy expended in the process is relatively modest.